>On Tue, 2003-02-11 at 07:21, Martin Collins wrote: >> On 10 Feb 2003 20:40:29 -0800 >> Florin Andrei <[EMAIL PROTECTED]> wrote: >> >> > What is the same typical image rescale for PAL? >> > 720x576 --> ??? - is it 720x540? >> >> Of the 720 width line only 704 pixels have image info. PAL pixel >> aspect ratio is 59:54 so to get square pixels you scale 704x576 >> to 768x576. > >That means you have to cut 8 pixels each from the left and the right >margins before rescaling?
More or less (slightly less), but only if you want to, of course. As long as you rescale by a 59:54 ratio, you'll get square pixels. If that's what you want. >What is the reason it is preferred to increase the size of the image >(from 704 to 768)? The information remains the same after all >(notwithstanding the interpolation noise). >Is it because it is preferred to have the final product in a standard >image size? The only reason to rescale is if you want/need square pixels. Unless a piece of graphics software is specifically aware of non-square pixel aspect ratio, it will assume that an image has square pixels. And if that is what you want, it is preferential to scale horizontally (even though it simply interpolates to create more pixels), because vertical scaling is complicated by the interlacing. It's always best to leave the vertical size alone with interlaced streams. -matt m. ------------------------------------------------------- This SF.NET email is sponsored by: SourceForge Enterprise Edition + IBM + LinuxWorld = Something 2 See! http://www.vasoftware.com _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
